Drilling set screw

Here is what I'm working on.

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1964 garden tractor. The wheel hub must come off before the brake linkage can be removed before the transmission can be removed, etc.

The hub is cast about 3/8 thick. The brake drum is bolted to the back of it so there is no place to hook a puller or anything like a bearing separater. The lug bolt holes are the only pulling points (5 on

4.5"). Problem is the 5/16 set screw.

I've tried drilling them out with what I thought were pretty good bits. I'm barely knocking the rust off. They are hard. I've used an allen impact driver to no avail. (good part is they don't strip out) There is enough meat to redrill and tap to larger size.

I can apply limited heat but don't want to be looking for nonexistant axle seals.

Once the set screw problem is solved, I can (reluctantly) drill and tap pulling holes closer to the 1" axle.

This photo looks dry but it has been flooded with JB Blaster for two months. An additional consideration is this is one of only two surviving. Suggestions?

Reply to
aasberry
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First time I heard of PB failing. If you do get it off, give us a review of what you think had it stuck so hard.

Steve

Reply to
Steve B

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My first choice would be heating with a TIG torch. Concentrate on the set screw and get it hot, red hot if you can. There is enough mass of iron there to save the seal if you stay on the screw. After it cools to about 300 to 400 deg apply 50/50 atf and acetone. Make no attempt to turn it till it completely cools off! When the screw is heated it will try to expand but it cannot and when it cools it will shrink to allow turning. HTH.... If you don't have TIG then try an oxy acet gas welding torch, single flame. Stay on the screw.... oh, I already said that.... phil k.

Reply to
Phil Kangas

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I have a couple of O/A torches. Do you think heating the screw will change the hardness enough to be able to drill it?

It is in at an angle so only one edge is contacting the key. If I can drill it, I think that thin edge might bend or break off when pulling the hub off.

Reply to
aasberry

I would not be considering heat since it is pretty easy to get to the set screw as as you say seals could make for an interesting search.

If you don't have a small carbide drill, then what about a small masonry drill with carbide tips? Check the local hardware store as ours has them down to 1/8" for drilling mirrors and tiles etc. Slow and steady and wd40 as cutting fluid.

Dave

Reply to
Dave, I can't do that

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Heat will soften it. Try a smaller drill first, stepping up in size. It may be possible that the screw is in a shallow hole in the key. That would secure the key from working out in service. Something to consider anyway. phil k.

Reply to
Phil Kangas

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Many set screws actually harden with heating - from my experience

Reply to
clare

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if it were me, I'd use Kroil for a bunch of days, then I'd heat the hub and when it is hot (but not glowing), I'd put a hex key in the set screw and loosen it (or if it's not a hex key, use whatever fits it) - the heat will expand the hub and tend to soften/break down the rust. If that doesn't work, let it cool and repeat with more kroil, some time, and try again

Reply to
Bill

I'm having more than a little trouble believing that. I'm not aware of any set screws being made from precipitation hardening steels, although I do suppose they could be. Beyond that, the only way the screw would be harder is if it was heated rapidly, heating only the screw, so the surrounding material behaved as a heat sink and quenched the material while the carbon was still converted. Sort of like a chilled iron casting. I'm having a problem with the idea that that happens, especially when heating by torch.

I'd suggest that a fast heating to a dull red heat would anneal the screw. Once annealed, whether it backs out or not (it may, for the heat will have also disrupted the rust that has formed), it will be dead simple to drill out. Drilling to the minor diameter of the screw should result in a clean hole with threads entrapped, like half a heli-coil.

Harold

Reply to
Harold & Susan Vordos

Im with you Harold . Never had a set screw harden when heated . The advice regarding spot heating the screw is good advice , I have used this procedure a number of times and it works .

Soaking in a good penetrating agent is also good , in conjuction with the spot heating

If you can get a left hand drill the minor diameter of the screw thread , some times the drill will grab and screw the screw out for you .

Reply to
Kevin(Bluey)

I wouldn't worry much about the seals.. there are lots of replacement styles, or even a greased leather washer (riding on a polished shaft) held by a sheetmetal retainer will work effectively at keeping dirt out. This is assuming that the lube is gear lube, not a hydro transmission (you said 1964 machine). You may still need torch heat to pull the hub, since the hub may not have been removed for decades.

The primary disadvantage is needing to use a handheld drill, which can attribute a lot to rapid drill point failure.. using a steady position and forceful feed pressure are going to be to your advantage. The drum should be secured so it can't rotate. If you can clamp a bar or other steady support nearby, it would likely help keep the proper approach angle and position.

In awkward positions and using a handheld drill, it can be worthwhile to take some time to fabricate a mechanism to apply more feed force and steady positioning using a lever to increase the feed force while offering a very steady feed direction.

In this situation, even a Cole drill wouldn't be a simple solution due to the drum size and the angle of the screw, but maybe something as simple as a section of chain and a lever pressing on the back of the drill motor would be appropriate.

The masonry drill suggestion could be a good solution, and for as cheap as they are, grinding them to suit your needs should make them even more effective for your needs. I'd suggest using a proper steel cutting lubricant, not just anything that's handy and slow RPM.

With a steady and forceful feed mechanism, using a pin and high RPM (no lubricant), friction may generate enough heat in the screw to soften it, but this method would likely be more appropriate for a workpiece on a drill press.

An air chisel used as a hammer, hitting on (a hex or mating) driver, with the hub supported by a steady hard backup like a jack stand on a cement floor (not a block of wood on soil) may be enough to work the screw loose while saturated with penetrant of ATF or miracle product. Hex wrench material and some hardened drivers are likely to shatter, so, the use of some fuel hose or other protective shroud would/should prevent shards of metal from shooting out and injuring the operator.. and uncommon sense should dictate the use of all the personal protection/safety devices/apparel required for safe practices. With a series of impacts the screw may dig into the key a bit more, relieving the holding grip in the key slot, and a couple/few thousanths inch of relief would be adequate to loosen the grip of ordinary square keystock, so a stable puller could pull the hub/drum off. Having the part removed from the axle will give you more options for dealing with the screw if it hasn't loosened to the point of just winding it out (or inward into the hole).

An annular cutter just larger than the screw diameter should effectively cut away the softer iron without dealing with the hardened screw. It looks as though you'd need to prepare a flat surface *like a counterbore around the screw hole) for the cutter to start on, with a die grinder (Dremel/Foredom etc).

I don't have a source handy, but these tiny holesaw-type cutters are available for cutting thru spot welds (although not particularly deep capacity) and other purposes. Woodworkers use similar centerless cutters for cutting plugs and dowels, so cutting cast iron with a quality cutting lubricant and slow speed may accomplish the desired results.

Reply to
Wild_Bill

If there is any way to get the correct bit in a hand operated impact tool, it would allow a quick tighten and loosen movement on the set screw. A tool like this:

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I know you can get a 3/8 socket drive Allen bit which can be driven by the tool.

Reply to
DanG

That is what I've been using. Mine is a little more heavy duty; 1/2" drive. Of course, I have to use a 1/2 to 3/8 reducer so I may be losing some torque in the extra joint. I'm twisting the barrel in the pre-loaded direction. The allen size is 5/32 so I can't get too heavy handed.

I went out earlier and heated them; waited until they cooled and smacked them again. No joy. They are now soaking in PB Blaster again.

If they are not loosened by towmorrow, I'll start drilling again.

Thanks for all the suggestions.

Reply to
aasberry

The vast majority of cup end set screws are either A2 or A4 steel - which is by definition an air hardening steel - and WILL harden when heated. Just like most exhaust studs. They are hard enough to start with, but if you heat them trying to get them out they end up as hard as glass. Very hard to anneal, particularly when jammed into a casting.

Works particularly well in maleable iron pullies etc, as it enlarges (in) the hole, then shrinks back, leaving a looser fit

Reply to
clare

Just checked on annealing A2 steel. You need to heat it to 1575 F and slow cool in the furnace at a rate of 40 F per hour or less. That's about 37 HOURS of cool-down.

Heating it in a casting and letting it cool WILL harden it.

Reply to
clare

Here's my strong vote for "heat and quench 3 times". I am sure you got the right idea from all the previous posts on this subject, but you need an OA torch with a really small tip, say a #1, in order to heat just the set screw. Get it glowing and have a squirt bottle of water handy. Once the set screw is glowing, squirt water on it until it is cool to the touch. Do this 3 times. Then, gently remove the set screw. A year or so ago I was faced with a couple dozen different kinds of stuck/broken off bolts in an Onan genset and I asked for help everyplace I could think of. The above was one of the suggestions I received late in the game and hadn't tried it myself until a few weeks ago. A guy brought in a front wheel drive car hub for bearing replacement. It had a sheet metal guard held on by 3 10-32 (or metric equivalent) screws that had been there since 1995. None of my normal stuff worked so I tried the above. It worked

3 out of 3 times. I am a convert. But, you have to be able to really focus the heat, I think. Note: one of the reasons you can heat the screw alone is that the rust/corrosion between the screw and the hub acts as an insulator so the screw heats faster than the hub (the hub having more mass). But, if you use too broad a flame, or a torch with a much lower flame temperature(think hardware store propane torch) the set screw will take longer to get glowing and the hub will be closer behind in temperature, so the set screw won't be crushing the rust as much.

See:

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you are interested in a range of solutions to this kind of problem. Long time lurkers: I haven't added to this page since Jan 23, 2010, when I posted its existence here.

Pete Stanaitis

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Reply to
Pete S

Both A2 and A4 are considered stainless---which, to my knowledge, is not the screw in question. I would fully expect that most socket sets are made of high carbon steel (which is, in fact, an *alloy*), which readily anneals. Could be wrong, but I can't find anything online to support the notion that they aren't.

I welcome anything you can provide to support your claim that they are precipitation hardening.

Harold

Reply to
Harold & Susan Vordos

Update. After heating, more PB, let it cool, still won't budge. 1/4" masonry bit took off just a little bit. Used a 3/16 punch in the socket a few licks. The allen wrench still fit perfectly but it won't move even a little.

The carbide bits I'm finding are for masonry, hammer drills or spearpoint for glass and tile.

Maybe I'll continue heating and removing a little at a time

Reply to
aasberry

I know of A2 and A4, IIRC 304 and 316 respectively so wouldn't be hardenable by heat treatment but I was wondering if he was referring to A2 air hardening tool steel. Not seen a mention of A4 tool steel.

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Reply to
David Billington

No, A2s and A4s are stainless.

That's what I'm talking about. And I've run across MANY setscrews over the decades that could barely be touched by a normal drill, and could NOT be touched by ANY drill after heating.

Before being heated, a good cobalt drill, at low speed, in a positive drive drill press, will handle most - but pretty hard to mount the garden tractor in the drill-press vice. If the drill spins instead of biting, the heat hardens the screw and you are DONE.

Same kind of steel as used on grader blades.

Reply to
clare

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