Boring accurate holes through 3mm box section…

[David SParticipant @davids]

Hi. I'm relatively new to all this and am attempting to build various workshop equipment in an effort to save a little money…To this end, i have bought a set of Myfordboys plans for his power hacksaw. My problem is this; How do i go about machining the holes through both sides of a piece of 50mm x 100mm x 3mm box section BMS to hold the bearing housing for the crankshaft. It needs to be square to the section, as that forms the body of the machine and so it's eventual accuracy will depend on this.

Many thanks, i look forward to your suggestions!

[David SParticipant @davids]

[JasonBModerator @jasonb]

What machines do you have available to do the boring on?

If you just have a lathe I would think fixing to the cross slide to drill and then finish with a between ctrs boring bar though hard to say without knowing the size of hole.

[BazyleParticipant @bazyle]

here is a video, chosen at random from a search, There are loads of pictures and probably a Myfordboy video too so probably someone on here has built one. It looks like the main base is that box section has about a 1in hole off-centre.

As Jason says it always helps to give a bit more information about the problem and what equipment you have. Even if you have in some other post detailed your life history you can't assume the readers will remember it or have read it. We are very helpful and quick to respond but we do need a bit of help in that too

If any of the suggestions that come along seem a bit beyond you, like not having a boring bar then ask for more details.

Finally if you can give an idea of the country and region, even nearest town in ou profile then maybe there is someone nearby who can help directly.

[BazyleParticipant @bazyle]

Still haven't looked at the video but don't worry about it being crucial for the accuracy. The design is such that you can have 4 goes at getting it right on the same material.

[David SParticipant @davids]

Ok, so i have access to a small chinese mini lathe and a vertical mill. The mill looks like a Warco Major type. The hole is about 1.660" from memory. I have a boring bar and a boring head on an r8 shank for the mill. I can't see a way to easily fix the box section to the cross slide. Hope this helps you to help me a little…

[David SParticipant @davids]

Oh, and i'm based up in Northumberland, though i use the workshop at the local Makerspace in Newcastle.

[Paul KempParticipant @paulkemp46892]

David,

Can you not clamp it to the table of the mill with a couple of packers under so the bottom face is clear of the table and then drill / open out with the boring head? Might take a while depending on what size cuts you can take but it should do the job?

Paul.

[peak4Participant @peak4]

Posted by Paul Kemp on 23/09/2018 00:13:25:

David,

Can you not clamp it to the table of the mill with a couple of packers under so the bottom face is clear of the table and then drill / open out with the boring head? Might take a while depending on what size cuts you can take but it should do the job?

Paul.

For cheap accurate spacers, pop into your local car repair garage.

The outers of bearings are accurately ground to size and make ideal packing pieces.

I've a selection of Landrover diff, and wheel bearing, inner and outer bearing races which double up as round parallels/spacers. let someone else do the hard work in making the packing pieces.

Bill

[Martin ConnellyParticipant @martinconnelly55370]

I would suggest starting off by machining two datum flats on one side of the box section. They need to be at the same settings and the minimum needed to give a good surface. Pick somewhere that is going to remain untouched through the rest of the manufscturing process and use them for all future setups.

Martin C

[David SParticipant @davids]

Posted by Martin Connelly on 23/09/2018 07:52:10:

I would suggest starting off by machining two datum flats on one side of the box section. They need to be at the same settings and the minimum needed to give a good surface. Pick somewhere that is going to remain untouched through the rest of the manufscturing process and use them for all future setups.

Martin C

Is that not going to cause a deal of chatter with 3mm thick steel? Or is it because it'd be such a light cut that this can be discounted? What tool would you suggest? I have 2 & f flute slot/end mills of various materials/dimensions and a small fly cutter i could use.

I did ask our mechanic to save the wheel bearing from my pick-up the last time we had a bearing changed, but unfortunately it got damaged in removal. It seems he doesn't keep old ones hanging around

[Martin ConnellyParticipant @martinconnelly55370]

Anything that does the job is the answer. If you clamp the part down it would be on suitable parallels under the datum faces so they may only be 12mm wide if using 6mm square hss blanks. If you turn the work through 90 degrees they only need to be wide enough for a square to be used or to run a clock against them or to clamp with parallels to a suitable vertical surface. It makes all the setups easier when you have to reposition for different operations.

Martin C

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