Help with Bench Top Drill Press "table jig" for chassis

[Willabe]

I'm having a little trouble with drilling out blank chassis. I bought a couple of Incra Rules. 1 - a centering rule, thats marked 0" in center, then marked in 32nds going 6" to the left of 0", and 6" to the right.  2 - a 6" T-sq thats marked 16ths, 32nds, and 64ths. There both very thin and have holes that are lazer cut to take a mech. pencile with 0.5mm lead at all the fractions. They cost a bit, but they work fast, and are perfect as can be on the lay out. I have a couple of good center punches and am not haveing any trouble with getting them centered on my layout marks.

I'm using a Delta 12" bench top drill press that has maybe an hour or 2 of light work logged on it. I'm using new drill bits, new step bits, and new greenlee punches. I'm using 3 in 1 oil, and have good lighting. Seems I should be good to go, but.....      a few of my holes are off.        

I had no problem cutting in the rect. (used a cut-off wheel on a dremel) and drilled the bolt holes for the lay down PT, it is darn near perfect.

The 7 pots on the face, when after I drilled them, I mounted them on the chassis and layed a straight edge across the pot shafts and 2 are off 1/16", all are the same pots, and the pot bushings fit nice and snug in there holes.
      
When the chassis was clamped laying down flat and drilled, all my holes came out perfect, but when I stood the chassis on it's side and drilled, some came out off as much as 3/32". Lets put it this way, I can see the 4 jacks don't line up and I can see the pots are not lined up! It's an alu. Marshall 18w from mojo, about 3/32" thick, (I can't find my dial cal. for the life of me) and the corners are not welded. It's a 4 input tweed 5G9 tremolux that I'm building, and I messed up these jacks and the pots on the face, I've got to do better then this. I'm using nice solid, nice sized wood blocks, cut to fit nice and tight with a table saw/power miter saw for support in side the chassis that I clamp in place along with clamping the chassis to the table.

I think I need to make some kind of clamping jig to better line up and clamp the chassis in place for drilling?

Like a right angle (L shaped) wood jig thats made out of a couple of 3/4" shop grade plywood pieces glued together, to make 1 1/2" x 1 1/2" thick L shaped clamp caul and clamp that to the table and clamp the chassis to the jig/caul. I am using an L shaped block now but it's only 3 1/2" x 3 1/2" @ 1 1/2" thick. I'm thinking it needs to be as tall as the chassis that I'm drilling for proper support for clamping to.

What are you guys using? I'm a carpenter and am good with my hands and tools, but I don't have much experence with metal working. I know I can do this if I learn more about what is standard practice in metal working.


              Thanks,   Brad                

    

            

        

[sluckey]

I just put a piece of 2" wide masking tape on the control panels, then use a machinist square and ruler to lay out the holes. Then I use an automatic center punch (sometimes I pop it 2 or 3 times to get a nice center mark). Then I drill pilot holes with 1/16" bit (size not critical) with the drill press belts set for next to slowest speed. Then use the correct size bit. If it's steel, I may progress thru 2 or 3 bit sizes until the hole is the correct size. I use a table-top drill press too. I very seldom clamp the chassis, and never clamp for holes that are 3/8" or less. I only use lube oil on steel.

If you get it laid out accurately, center punch accurately, and use a small pilot bit, I think you should get good results. Hopefully there is no side play/wobble in your chuck.

[stingray_65]

I've worked a lot of sheet metal, LOTS!

Generally when working in sheet metal, it pays to give a wider tolerance.

In most non- critical metal working, +-1/64" is the norm. In sheet metal work +1/16 -0 is the norm.

Problem is when drilling sheet metal, the tip is guided by itself, and only has the thickness of the sheet metal in contact with the drill tip.

A particle board backer board helps a lot. It's hard enough to stabilize the drill and as a bonus it reduces the burr on the backside a lot. Pine is too soft to keep your drill in line and Oak's grain can pull your drill! even a 3/8"!

Your "pot holes" should be 1/32" bigger than the shaft. Actually all your "through holes" should be. this will help in your alignment.

When using a knock out punch, the hole you drilled for the pull stud can wonder as described earlier and any slop can be compounded more depending on where the pull stud centers.

The trick to making rows of punched holes nice and in a row, drill your stud hole bigger, and just finger tight the stud until the receiver and the die touch the chassis. now measure the distance from the die to the edge of the chassis,and snug it till the die bites. I usually  will scribe a line  and align the outside of the die to the line.

If you are punching holes for a tube socket, punch the hole first, then use a socket to mark the mounting screw holes. That way if you are off laterally your screws will still line up without having to "egg out" the big socket hole.

Step bits are great, but I've had them more than once "load up" on one flute. What happens then is the drill starts to cut eccentrically, then the next step does the same thing, only it can be in any direction.

In general, I do not use a drill press for sheet metal work, I use a cordless drill. Reason being, a chassis is to thin to notice if a hole is drilled in to it on an angle. And as I drill I can see if my bit is wandering and I can maneuver my drill motor  to bring it back in line.

A big help here if you haven't developed an eye for that sort of thing, Use a compass to mark the hole after it is center punched. It doesn't need to be spot on as far as the diameter, It's there to help you see if you're wandering.

These are all "tricks" I've used and still do.

One of the HARDEST tricks to do is to RELAX! NOTHING IS PERFECT!

You might see the "error" or lack of tolerance, but I bet if you're close no one else will.

Get this, I have a CNC mill and have made chassis' spot on with a tolerance of +-.0001", and have had components not fit because of the manufacturers lack of precision!

Ease up, if it looks good in the end, it looks good, just be sure to ask someone elses opinion besides your own.

Ray

***EDIT***

Some layout tips:

Most chassis are not very square. Because of that only measure from one side, Only use your square off one side.

Sluckey has a good tip in using masking tape. Also good for preventing scratches as you machine the chassis,

I also use a magnifying glass when I use my center punch.

I also multi hit my center punches, BEWARE you can move the metal around when center punching!

[Ritchie200]

The biggest mistake you can make is use a typical chisel point drill bit.  The leading edge is usually 2-3 times wider than the center punch and it has a tendency to wander a little before it settles in - which is why a small pilot hole slightly larger than the chisel point width works well.  The best bits to use on sheet metal are brad point bits.  You can free hand it with a hand drill and the points will pick up a center punch.  The best part is - no burrs.  Another type that I will use in a pinch are cobalt bits.  They typically come with a four facet or modified split point grind and will pick up the tiniest center punch.  If you use a backstop (like I do), you can just slide the chassis down to each penciled mark and it will drill right where you put it.  The FF or MSP will not wander, unless you lean on it!  I used to clamp my chassis to a backstop on my Bridgeport and crank to each position and bore using center cutting end mills.  Now I just use a drill press or hand drill with brad points - too easy.  Hope this helps!

Jim

[Ritchie200]

Sorry, yes, my backstop is a tall as my chassis, actually taller.  It's an old slotted cast iron angle plate on the mill.  I've got a 6x6 granite angle plate that I use on my drill press.  You just want to make sure it is supported.  I think your problem has more to do with the drill wandering than the support.  Although an Al chassis that is not corner welded might wave in the wind a little!  Again, if the bit bites where you want it, the chassis will not move.

Jim

[Willabe]

Thanks guys.

I wanted to soak in and think about what you guys said before I wrote back.

Then I use an automatic center punch (sometimes I pop it 2 or 3 times to get a nice center mark). Then I drill pilot holes with 1/16" bit (size not critical) with the drill press belts set for next to slowest speed. Then use the correct size bit.
If you get it laid out accurately, center punch accurately, and use a small pilot bit, I think you should get good results. Hopefully there is no side play/wobble in your chuck.

The biggest mistake you can make is use a typical chisel point drill bit.  The leading edge is usually 2-3 times wider than the center punch and it has a tendency to wander a little before it settles in - which is why a small pilot hole slightly larger than the chisel point width works well.  The best bits to use on sheet metal are brad point bits.  

My lay out is right on the money, those Incra Rules are working great for me, so easy and much faster than anything I've ever tried for lay out before. I hit the center mark cross hairs once with the center punch and then check to make sure it's - exactly - on my mark, then hit it a couple of more times. Also I found if it's not - exactly - centered on the cross hair marks, I can move it slightly by tilting my punch pointing in the direction it needs to go and hit it again. This part I think is fine.

I think where I'm going wrong is I'm using an Erwin 3/16", 135 deg. chisle point bit (got the set at home depot) for my pilot hole because the pilot on my step drill is 3/16". Also my drill press is a 5 speed (620 to 3100), and I was using the highest speed. What speed/s should I use?    

I'm going to try the brad point bits, they sound like a good option. I seem to remember seeing them at the big box stores, If not Rockler and McMaster-Carr have them.
I'm also going to make a fence/back stop thats the full hight of the chassis. I can bolt it to the slots in the table and use a couple of those screw down fast action lever hold down shop clamps.

When using a knock out punch, the hole you drilled for the pull stud can wonder as described earlier and any slop can be compounded more depending on where the pull stud centers.The trick to making rows of punched holes nice and in a row, drill your stud hole bigger, and just finger tight the stud until the receiver and the die touch the chassis. now measure the distance from the die to the edge of the chassis,and snug it till the die bites. I usually  will scribe a line  and align the outside of the die to the line.If you are punching holes for a tube socket, punch the hole first, then use a socket to mark the mounting screw holes. That way if you are off laterally your screws will still line up without having to "egg out" the big socket hole.
These are all "tricks" I've used and still do.
One of the HARDEST tricks to do is to RELAX! NOTHING IS PERFECT!

Ray, you and Ritchie both mentioned using a hand power drill, I'm gonna try that also.
 
I've not had a problem with any tube sockets, - yet -, but I did stumble across the option of using a larger pilot hole and finger tighting the knock out punch in place and it does work great. And yes, I'm punching the socket first, then go back and use the tube socket to mark the mounting holes. It's been working great also.

One of the companys I worked for as a carpenter years ago made me their punch list guy for a year or two, and I've finish trimmed and tape a lot of dry wall also. I had to fix/make right just about anything to everything or the boss did'nt get the last payout from the job. So I still have a hard time relaxing if some thing I do is not right. Your right, most people wont see it, untill you point it out to them, but I do. My wife still finds it funny when we go some where and I'm looking around at all the "lines" in the room, doors, windows, trim, cabinets, hardware, outlets, paint jobs, walls, ect... I don't do it on purpose.      

Any way thanks guys for the input. I think all of it will be very helpfull to me!

I knew you guys would set me straight.    


         Thanks,    Brad            
        

        

[stingray_65]

Hey Brad,

I have to say it, but you probably already know it.

When ever you make something, you get better as you go and do more of them.

I look at the lines in a room too, most of the mistakes or faults that I can pick up are the mistakes I've made before.

I'll bet a dollar to a doughnut that the next chassis will be even closer yet.

If you're anything like me, I feel my work should be as good as the guy who's been doing it 20 yrs.

Ray

[Willabe]

Thanks Ray. I belive what your saying is true. I will get better, and the next one will be better.

My first mistake was I should have practiced on a cheap/small chassis first         and I know better.

most of the mistakes or faults that I can pick up are the mistakes I've made before.

Yep, thats very true. You can't help but see it. My wife is a home health care nurse and she was talking to a patient's wife the other day while visting him, he was a carpenter. So the guys wife say's they had dinner at a friends house last week and as their eating the carpenter says to his dinner host's "the knob on that cabinet door is off center"  

The man had lived in that house for 20 years and never noticed it before. The guy lost it and was very upset for the rest of night with his dinner guest. The dinner guest says "It's been like that for 20 years, what's the differance." "Because now I'll see it!"        

If you're anything like me, I feel my work should be as good as the guy who's been doing it 20 yrs.

Yeah just because I can play guitar does'nt mean I can just pick up a mandolin and play it just as well, right off the bat with out practice. Some things are the same, both have steel strings and frets but there's more to it than that. Same thing with tools and working with different materials.          Still need to practice.


               Brad        


  
  

[Ritchie200]

Yeah just because I can play guitar does'nt mean I can just pick up a mandolin and play it just as well, right off the bat with out practice. Some things are the same, both have steel strings and frets but there's more to it than that. Same thing with tools and working with different materials.          Still need to practice.

That's not true!  I play a lot of old tunes that my kids think are a little off!  Sounds good to me tho...  

As a caveat I hand drill holes VERY carefully.  Again, if your holes are off, it may look like the bit picked up your center punch but as it starts to bite it has to be pulling or it would be spot on.  That is the beauty of the brad points, they easily pick up the center punch and drill outside-in.  That is all I use for pot holes.  But as Stingray said, practice makes perfect.  If anyone says anything, tell them that all the boutique amps look like that!  It's that hand built look!

Jim

[overtone]

...That is the beauty of the brad points, they easily pick up the center punch and drill outside-in.  That is all I use for pot holes...

I was feeling guilty using brad points for drilling sockets in aluminium because I thought they were only for woodworking.
Do you have ones made for metal working in the USA?

Best, tony

[jjasilli]

This thread caught my attention:  checkout these brad point sheet metal bits:  http://www.wlfuller.com/html/short_length_brad.html

[Willabe]

This thread caught my attention:  checkout these brad point sheet metal bits:  http://www.wlfuller.com/html/short_length_brad.html

Thank You Sir!   Nice find.      


        Brad        

[Ritchie200]

Most are made from high speed steel or better (some come TiNi coated) and even the no-name mystery metal bits from chine will probably last a good many holes in aluminum or mild steel.  I'm not sure you can find these in the big box stores, but all the tool supply places have them (McMaster Carr, etc.).  Be wary of the deep discount import stores.  I looked at some value priced regular bits at Harbor Freight and the grind was so far off, I don't see how they could have worked - much less drill a hole to size.  You get what you pay for with tooling...

Jim

[Willabe]

If anyone says anything, tell them that all the boutique amps look like that!  It's that hand built look!

                   I bet that would work!                Gotta go, gotta practice some more, gonna be a  cajun zidico blues man                        Ieeee....

Hey, save some'a that crawfish for me!       


                             Brad                  

[Bub]

One thing to try is cutting oil, which is meant to grab, 3 in 1 is meant to slip. Probably to late on this post but for next time.
Hope this helps

Rob

[DummyLoad]

yes, you can cut aluminum dry but your tooling will last much, much longer with lube & cooling. for cutting aluminum your 3-1 is better than nothing - just use more as it cooks off faster then cutting oil.

about any machining process...it takes patience and diligence; the moment you start getting in a rush is when things go to hell quick.

heavy gauge food wrap, masking tape, or painters tape helps to keep scratches by the machines and tooling to a minimum. it can also be your cutting/drilling/punch guide.

print and use paper drill template(s). tape them on to the work and use them as your guides.

drill bits - the dewalt pilot point bits rock. they are best general purpose bits i've ever used. use a quality tool - life sucks when cutting with a dull tool, even worse when a cheap tool that dulls quick is thrown into the mix.

if your drill press has T-slots may i suggest building a fence for it - that way at least on one axis your work won't waver much, if any.

secure your work to the table if at all possible. machine tool cutting is nothing more than a controlled tear - do you really thing that you can hold back the torque of a drill press motor, much less try to work against it? no, you cannot. use aids.

clamps and backing board are your friends - use them if you are able to. if you clamp to a fence like the one shown below, aligning the work is a bit more difficult, but with practice you'll get the hang of it. for backing board use hard pine or oak. softer woods are nothing but grief unless you're using them as a buffer.

make sure the table is clamped well to the pillar. a table that's wobbles while cutting makes for nasty holes.

in the photo's below, i made the fence out of 1" x 2" bar stock 6061 aluminum. the fence clamp screws are made up of 5/16" square nuts for the table Ts (slots), a couple of short sections of 5/16" all-thread rod, and a pair of 5/16" wing nuts.

y'all are probably going to laugh...may i suggest you get a magnifying glass and use it help center the bit over the punch mark or cross hairs of your template. i get exceptional accuracy that way.







 

[overtone]

Thank you everyone for all the information so far. The photos are really helpful too because I was imagining a fence to be kind of safety cage... back in England I think we called it a guide. I am going to rig me up one of those fence guides.
Before doing metal work now, I take my time, pick a calm day and the right moment, all Zen like, and the results are already better!

[Willabe]

OK, I just did a 4 hole Fender tweed type input and it came out darn near as perfect as it can be. I'm pretty fussy and I am very happy with it.

I used brad point bits, 1'st a 3/32" then a 3/8". I got my center punch marks right on the money and drilled out the holes with my bench top drill press.  

Took about 4/5 tries till I came across something that worked for me, as far as different bit sizes.

The 3/32" is/seems to be about the same size as the 3/8" bits brad point. It's the smallest brad point bit I have.

No burr to speak of, which cleaned up with a few turns of the little deburring tool's hook, all the way around, I'm very pleased.

I know it's only a start and I need to gain a lot more experience, but that should come with time and practice.

Was starting to think I wasn't gonna figure it out even after all of what you guys shared, but I did it!    

Thanks again to all of you for sharing your experience of drilling out chassis and metal working!!!        


            Brad      



Went back just now and enlarged the input jack holes with a uni-bit from 3/8" to 1/2" to add the nylon insulators, and it worked perfectly.        

[PRR]

from:
Jigs, Fixtures, and Shop Accessories
R. J. De Cristoforo
ISBNs: 0830642102 , 0830642110

[Willabe]

Thanks PRR,

Seeing those pic's jogged my memories and I went down stairs and found a 1991 copy of "The Drill Press Book" by R.J. De Cristoforo.

I had completely forgotten I had it.             I'm pretty sure I have a copy of " Jigs, Fixtures, and Shop Accessories" around somewhere, I wonder where I put it?              


       Thanks,   Brad      

[PRR]

De Cristoforo is best known for woodworking; many chassis jobs are similar to drilling blocks of wood (except break-through is MUCH more violent).

[Willabe]

Hi all,

Well I made a nice little fence for my drill press table, and so far it works great.

I had some cut-off's left over from the work bench I had made for myself last fall. I used 7 ply, pine, no void, A/A, ext. glue, ply wood. I glued up, 2 > 3/4" strips together with Titebond 2, "they call it weather proof", you can use it for deck chairs, bird houses, etc. but not for boat hulls. It was already riped to 3" wide, cut it to 19" in length, drilled a couple of 1/4" holes for the carriage bolts and used 2 of those 5 pointed/star black plastic jig knobs they sell at wood working stores. Had to add 4 > 1/4" fender washers to each bolt as spacers to be able to tighten the fence bolts all the way down through the tables T slots.

I'm still thinking about adding an indexing jig to the fence. Trying to figure out how to make it so there's --- NO --- slop in it. Would be nice to drill a line of controls with it, but it's not a must.

Thanks again to all for setting me strait and pointing me in the right direction.


           Brad                   

     

[Ritchie200]

Just cut some blocks to your spacing size, set a stop for your first hole and start adding blocks.  I'm a scribe and centerpunch kind-of-guy.  I wanna see what its gonna look like before I start making chips!

Glad it all worked out for you!

Jim

[Willabe]

Just cut some blocks to your spacing size, set a stop for your first hole and start adding blocks.  Glad it all worked out for you!

Yeah, I thought about that as an option. I might try that.


             Thanks, Ritchie


                           Brad