Drill press restoration - Zapins

Oh my damn. That seems to have a high skill cap. Alright well a set of Starrett gauges is on my list to get. That and a machinist level

So I used the tailstock alignment bar to sort out my tail stock. Its dead nuts from side to side but top to bottom it is within 1 thou and when I rotate the center it seems to go back to perfect alignment. So it seems to be within 0 to 1 thou aligned up and down. This is over the entire length of the 12 inch bar so I think that's alright for now.

I had to shim the tailstock up to 15 thou. Quite a lot of wear. I still think it needs another half thou shim to get it exactly bang on. The shims are stacked like 8 sheets deep as I slowly figured out how many thou I needed. So I'd like to buy one sheet of 15 thou thick shim then a half thou and get it to 15.5 for perfection.

Next I'm going to see about grinding my 3 jaw chuck to get it perfect. So I can switch parts in and out without misalignment. The goal is to go from 5 thou out on the chuck jaws to 0.5 thou or less out.

By that time my 4140 shaft material should be here and I can start prehardened it and cutting the shaft.

I might still end up cutting it between centers just for accuracy but will see what I can sort out.

Another interesting issue I found is when ordering cheap bearings off Amazon in 10 packs. They arrive but don't fit the original shafts that came with the machine. They are too loose and don't press fit in. But when I buy expensive brand name bearings they fit perfectly. I'm guessing thats because the cheapos are knock offs and have wild card tolerances?

 

These Lufkin Gages look like a good set that will cover 98% of bores you will ever need to measure for 44 bucks. Measuring bores over 3 inches will be a rare occurrence.

https://www.ebay.com/itm/265149459137?hash=item3dbc23aac1:g:U-gAAOSwdr1gkrd-&LH_ItemCondition=4

Denis

 

Mystery bearings are just that, anything from an unusable bearing shaped object right through to a decent bargain product. A ball bearing that is pretty good bang for buck is the NSK "CM" clearance or "clearance motor" bearings. They are tighter clearance and a bit more precise compared to CN or "clearance normal" bearings but cost about the same. The "CM" radial clearance specs are on a different page in the NSK manual so I've had bearing shop counter staff argue that they don't exist .

 

It’s a practice thing. I don’t think there’s any way around it. There are times when I could use a set of those telescoping bore gauges, but for me they would be more to check consistency of a bore from one end to the other (springy boring bar, etc). They’re on my wishlist. I have a nice set of micrometers in various sizes up to 6” I think, which have that slipping tightening knob thingy (excuse the technical jargon, lol), and that is helpful and reassuring, but there’s no such thing on the calipers. I sometimes have those exact doubts when using them, especially when measuring inside diameters. I’m more comfortable with my pressure on outside diameters because I’ve actually practiced on a piece of ground 1/2” rod that I keep on the bench that is spot-on .500” with my cheapo calipers. I don’t have a known standard for I.D.s but I should get something to practice with. Santa brought me a new Mitutoyo digital caliper for Christmas so I’ve got some more practicing to do.

Pete

 

Some golden rules for different fits;
1. Make sure to allow for temperature difference between the two parts, when measuring them. There is no point measuring a hot part in the chuck, if the other piece is at room temperature. This might mean leaving the parts in the same room for several hours until they reach equilibrium. The ISO standard for measuring temperature is 21C, I think.
2. Decide before you start machining, what type of fit is needed and check a fitter's handbook to see what the suggested dimensions are.
3. All surfaces to be measured should be smooth and clean, as should be the measuring tool. On the part, this might mean sanding to the final size.
4. Use the best quality measuring tools such as; Starrett, Vertex, Mitutoyo, Moore and Wright.

If you don't want to buy telescoping-gauges, you can make go-gauges and no-go-gauges, to simulate the parts. For example; you have bored a hole, which appears to be to size of 1" diameter. The hand book says 0.002" interference fit, so you then turn a dummy shaft to 1" diameter; it should slide into the hole perhaps with a little encouragement. If it definitely does not want to go, the hole needs honing.

When the go-gauge is sliding into the hole, the no-go-gauge which is 1.001", is used to make sure that the honing has not enlarged the hole too much. If all is well the actual part can be turned to 1.002" knowing that it will press in nicely,

Cheers Charlie

 

I'll have to look up honing and how to do it properly. I'd like to be able to make accurate parts when needed. Half the issue is I have one chance at cutting a correctly sized part sinc either cant put it back on the lathe and have it be centered enough for another cut with my 3 jaw so out of alignment.

I did however start making a holder for my foredom so I can do some grinding inside the chuck. I saw a YouTube video where the guy relieved the back of the jaws by letting them spin in the chuck open just enough that he could then clamp the jaws around a bit of metal in the relieved area. That allowed most of the length of the jaws to remain open to be ground to shape while still applying pressure from the right out to in direction. Seemed to let him get his chuck to half a thou accuracy.

 

Please do yourself a favor and do a search on "Practicalmachinist grinding chuck jaws"

Five or six threads will show up. Read through each post on all of them.
The guy on Youtube has to be full of it.

It may be possible to improve the chuck in some regards. A brand new highest quality 3-jaw will not be accurate to .0005" over it jaw range. It might be (by some luck) at one opening. Too many moving parts and surfaces to make them to that sort of tolerance and certainly after a scroll has been in service a while it will have nothing like that kind of accuracy.

You can fit a 3-jaw with soft jaws and machine them carefully using proper technique to fit a part or run of identical parts to high accuracy for that single application. But I do not think that is what you are wanting.

Denis

Denis

 

Thats true. Well hopefully the grinding improves the jaws a bit. At least in the 1 to 3 inch range that most of my projects fall into.

I did more work on the drill. Cleaned up and blasted off all the old gunny paint. Then went ahead and spray painted some of the bits. I think they came out rather nice.

I took apart the splined insert that let's the shaft slide in and out and let's the pulley transfer power to the spindle. Pretty interesting that they have 2 bearings at the top. I would have thought 2 bearings would be better at the bottom nearest the chuck for stability when people inevitably use the chuck for things they shouldn't be doing.

Anyway. What are the T shaped cut out shapes for in the base plate of the drill? It looks like something could be attached to this square area with a slide or something?

 

They’re t-slots for mounting a vise or fixture for when your work is too long for the regular table or if the table is otherwise unsuitable for the work. They’re also handy for dropping small parts into.lol.

Pete

 

That 3/32 drill you were missing....in all the swarf under there. I regretted not making a cut out under mine before bolting down.

 

And should be used to clamp down work always when drilling or boring. The drill press is a very dangerous tool though it may seem benign. Lots of bad injuries from work spinning on a drill and flailing the operator. By bolting down the work or a backstop for the work that risk is eliminated. I don’t mean to be the safety police, but the drill press/mill is often way underestimated with respect to safety.

Denis

 

I can not agree more with Denis on the subject of safety and clamping the work securely.

Buy a clamping kit, you will never regret it,
https://www.cltoolcentre.com.au/haf...ODXhZRrI3gkjooCLFxhPUG1QjA0JnJQhoCiNYQAvD_BwE

Cheers Charlie

 

Neat kit. I'll have to youtube how people use it.

I've had a couple spinning wheels of doom on the drill press but not too bad. The bench grinder has nailed me most often it enjoys eating the skin over my knuckles most.

I made new handles for the drill press today (and painted them) but I enlarged the diameter of the steel by about 40 % from original design to hopefully prevent bending during use. Also please admire my new lathe threading tailstock tool. Its freaking fantastic and I don't know how I lived without it.


I also made a holder for my foredom which I plan on using to regrind my chuck jaws. Still need to install set screws however... I need to finish the drill press project first....

 

So I'm bumping into a bit of an issue. The bottom bearing closest to the chuck has different options which allow up to 20 mm wide inside bore using the existing bored hole in the iron casting. However at the very top of the drill press where the bearings attach to the pulley it seems that I cannot find any bearings 40 mm diameter except 6203 bearings with 17 mm inside bore or the very expensive non standard vxb brand 25x40x9/10 bearings https://www.vxb.com/Non-Standard-Special-Sealed-Bearing-25x40x9-p/25x40x10-bearing.htm or needle bearings (not sure if those would work for this application at all?).

But basically that leaves me with two options - pay $100 for two nonstandard bearings and enlarge the splined part of the spindle or just replace the original bearings and cut 12 mm diameter splined shaft (basically remake the original spline part).

So if I make the splines 12 mm then I'm not sure what would prevent them from twisting like the original part did. But I could reuse the original female spline part if I did that so that would be nice. Do you think the new 4140 shaft splines will twist like the original mild steel shaft? Am I over thinking this?

 

A 6004 bearing is 20mm bore and 42mm O.D. so you could open up the original bore to 42mm from 40mm. Also 4140 in the normalized state is roughly twice as strong as mild steel from memory so it would be more than up to the task of a drill press with a sub 750W/1 HP motor.

 

I'm not sure I have the tools/ability to open it up to 42mm. Maybe I will just have to cut the shaft splines to 12 mm. The rest of the rod will be 20 mm. So hopefully that prevents the jacobs bit from being bent.

I'm going to try temper the rod tonight. It arrived in the mail

 

That bearing spindle housing is an iron tube with a gear rack cut up the side?. One way to improve accuracy of your lathe would be to make a single use mandrel from scrap to sit the drill press spindle housing on. By machining a male shape to fit one bearing race of your spindle tube inside on your lathe and never removing it from the chuck, you sidestep any chuck wear and concentricity issues as you know it will be as concentric as your lathe spindle bearings allow. You slide the tube onto the mandrel and Loctite it in place and carefully machine the new bearing race and this ensures good alignment of the two bearing races: they are on the same axis and concentric relative to each other now. Once you are done, you heat it up gently with a torch and and above 130 deg C the Loctite lets go and releases the casting.

This steel mandrel lets me machine the two bearing bores of the casting in alignment (accurately enough for the two bearings tolerances). As it's machined in the lathe and not removed until all work is done, it's perfectly lined up for a single use.



This second spindle housing casting is too big for the mandrel but you get the idea of where it
fits.

 

Can I cut 1 mm off the bearing itself with carbide cutters?

I like the idea of a mandrel but the bearing seat I'm talking about is the one on the body of the iron drill press not the spindle tube housing with the slots cut in the side.

Its the square hollow cast that I brazed to repair the crack on the bottom. The top hole has the seat for the 40 mm bearing. That would need to be cut to 42mm.

There are apparently some smaller bearings that have a 25 mm bore but the outside diameter isn't 40 mm its 37mm so if I have a shim or something like that I could seat the bearing into a sleeve inside the 40 mm bore? Would that work?

 

If that's the case, then making the shaft in 4140 and getting the benefit of the extra strength is all you really need. Ball bearings are usually stronger than the shaft that fits up their bore anyway not to mention this probably has a 3/4Hp motor at best.
A 6203 bearing handles 975 Kg radially and 490Kg axially according to the NSK manual.

I've seen the outer races of tapered roller bearing machined with carbide or ground with a toolpost grinder to size where concentricity wasn't an issue to make a metric tapered roller bearing into an imperial outer for Harley Davidson forks or on old USA made earthmoving machinery as a desperation move (still in place 10 years later). This was relatively small amounts of under a millimeter removed.

 

Might be easier to just do splines 12 mm and bottom of the shaft 20mm then. That way with the added strength of the 4140 the splines won't twist and the chuck itself also won't be able to bend.

If I remade the spline part thicker then I'd also need to remake the female spline coupler and also enlarge or replace the pulley since the bore was made for 12 mm.