Drill press for cutting 16mm holes

[ChaiLatte]

An interesting idea but the link is for use on a scroll saw and will be exposed to constant wood dust.

Please could you clarify whether the linkage is reciprocating rather than rotating?

For a rotating device, the bearings will be OK.

If it is (only) reciprocating, bearings might not be so good as there would never be 360 degrees of movement in the bearing and in that case, rose joints or plain oilite bushes may be better. It is possible to buy rubber dust boots for rose joints.

The only "problem" is the lateral distance between the two bearings (AND getting them both on the same centre line)

We would need more details from the OP, but if it is just a single linkage, with one only used on any particular machine, the absolute value of the distance between the bearings is not so important nor, within reason, is the position of the holes relative to the surrounding material.

For links used in pairs, the hole centres of the two items must match, to be sure, so there is no binding.

 

[Yorkieguy]

A step drill will perform that task smoothly, quickly, and with no dramas. I have a set which I use often. They're widely available cheaply. Ordinarily UK Drills, which is my 'go-to' form for all all drills stock a set of three which range from 4 - 32mm but are out of stock just now, though they do have individual step drills. EG, code 33.4209.1, which is 4 - 20mm in 9 steps, for just £6.95 inc VAT:

https://www.ukdrills.com/hss-step-d...Vji6BBYMfTKoxMOSCH40_LO_3QJzoafhoCVtIQAvD_BwE

The depth of cut for each step is 6mm on mine - each step is angled slightly inwards to prevent jamming. If the 16mm drill doesn't quite go right through the thickness of the plate you which to drill, you'd just need to turn the plate over and drill the last mm or so from the other side, which it would do in a jiffy, smoothly, and without any chatter.

I had a chum who wanted to make some 22mm and 32mm holes in a piece of 2mm thick aluminium plate. He was going to drill 5mm holes around the perimeter, remove the scrap then file the hole to the finished shape with a half-round files, as he put it 'in the traditional way'. I suggested he bought a step drill, but he was sceptical. I drilled a couple of holes 22m and 32mm diameter in a piece of scrap 2mm plate and sent him a pic, which I've attached. No burr - nice clean holes, literally a two or three minute task. See pics below.

Occasionally a hole may be needed which is between steps. For example 21mm, where the options are either 20 or 2mm2. In many cases a 22mm hole would do fine, because that's only 0.5mm oversized around the perimeter (about 2.5%) . If it was critical, using a 20mm step and filing 0.5mm around the perimeter of the hole wouldn't be an arduous task.

Incidentally, if a 16mm conventional drill bit was used, the hole wouldn't be exactly 16mm - it would be slightly oversized.

Just my thoughts.

Good luck with it.

David.

 

[user 42626]

Please could you clarify whether the linkage is reciprocating rather than rotating?

For a rotating device, the bearings will be OK.

If it is (only) reciprocating, bearings might not be so good as there would never be 360 degrees of movement in the bearing and in that case, rose joints or plain oilite bushes may be better. It is possible to buy rubber dust boots for rose joints.



We would need more details from the OP, but if it is just a single linkage, with one only used on any particular machine, the absolute value of the distance between the bearings is not so important nor, within reason, is the position of the holes relative to the surrounding material.

For links used in pairs, the hole centres of the two items must match, to be sure, so there is no binding.

Its a drive link between the saw arm and motor

 

[Fergie 307]

The OP doesn't make it clear, but I assume these parts are to be sold to Hegner owners? If I were buying a bespoke part for such a machine I would expect something properly made, certainly not bearings held in with Loctite. For your own machine fair enough, but not if you intend to sell them. As ChaiLatte says if the two shafts are not exactly aligned your bearings will not function or last well, oilites might be better, and would be much easier to fit.

 

[Fergie 307]

Ok now seen the image of what it actually is for. What does the original part look like, and what are the issues that lead people to want to replace it?

 

[user 42626]

The original is nylon plastic and the bearings either wear or begin to seize over time, as little as 4 years with heavy use. This then leads to cracking or ovalling of the holes. The crack is always bang at the tips so I figured a slightly oversized version is worth trialling long term.

 

[ChaiLatte]

certainly not bearings held in with Loctite.

That is not a great argument. Loctite sell the product specifically for this exact application. There are thousands of commercial products that use the same technique.

Loctite sell gallons of it daily because the cost of their product is less than the cost of manufacturing to tighter tolerances.

FWIW, I did not say anything about the shaft alignment: only that if two links are used, the hole centres in both must match.

 

[ChaiLatte]

The original is nylon plastic and the bearings either wear or begin to seize over time.

OK. As above, it looks like one of the bearings is rotating (the one attached to the motor) and one is only rocking back and forth (the other end of the arm).

Bearings live for a long time when they go round and round. They do not like going back and forth repeatedly as the wear, friction, heat is then only spread over a small part of their circumference.

Is it always the non-motor end of the arm that cracks? Is it always the non-motor end that seizes?

If that is so, it would seem that a simple solution is to reverse the arm every year. At worst, you would double the life of it. You could always replace the bearings at the annual oil change and tyre-kick.

If the root problem is the bearing failing, a new arm is not going to solve that issue.

 

[user 42626]

I've worked with these saws for over 30 years, servicing and rebuilding them. The wear pattern is irregular.
I have about 30 saws stored that I'm refurbishing over time and I'm looking to trial a better link out of interest. The genuine part is now around £50. The part is nothing spectacular and lets not forget it function is quite rudimentary.
The bearings used will be top quality ones, skf, fag, nsk, etc. The saws are always built to high standards. If it's possible to create a link then great but as like many things opinions vary and judgements harsh at times. I'm not looking for negativity, just options worth trying, after all its my time, my risk.
I'll continue my efforts, I will be buying a drill press anyways as its required for other jobs

 

[Phill05]

"If that is so, it would seem that a simple solution is to reverse the arm every year. At worst, you would double the life of it. You could always replace the bearings at the annual oil change and tyre-kick.

If the root problem is the bearing failing, a new arm is not going to solve that issue."

Sealed for life bearings and weak Nylon arm breaks replace Nylon with aluminum, he knows what he is doing is correct.

 

[Cabinetman]

I’m not an engineer so this is only an idea, would it be possible to put the 80mm long piece in a "shoe" on a faceplate and turn the holes on a lathe? Once set up the cutter wouldn’t need to be altered maybe.
Ian

 

[user 42626]

I’m not an engineer so this is only an idea, would it be possible to put the 80mm long piece in a "shoe" on a faceplate and turn the holes on a lathe? Once set up the cutter wouldn’t need to be altered maybe.
Ian

Interesting idea but my original question is I'm looking at buying an old drill press and advice/options to drill a 16mm hole to hold a bearing
Thanks for the suggestion though

 

[Fergie 307]

That is not a great argument. Loctite sell the product specifically for this exact application. There are thousands of commercial products that use the same technique.

Loctite sell gallons of it daily because the cost of their product is less than the cost of manufacturing to tighter tolerances.

FWIW, I did not say anything about the shaft alignment: only that if two links are used, the hole centres in both must match.

Not sure I would trust the Loctite in this application, narrow bearing in a through hole rather than a pocket. In any case it's about quality, if you are going to do it, do it right. Only ever used the Loctite in old machines where housings were a bit iffy.
In the OP's case I would say 4 years for a bearing like that, in that application is probably not unreasonable. £50 for the part is outrageous, so I can certainly see the attraction of making replacement ones in alloy.

 

[Fergie 307]

Might be worth trying a 5/8 drill 15.88mm so, given the hole will be slightly larger it might give you a hole the bearing would go into, or start with that and buy a suitable adjustable reamer to take it out a little more. Quite Labour intensive, but at least once you have the reamer set up you can repeat.

 

[imageel]

I too am no engineer but it seems to me that as others have stated, a bearing used in this configuration where perhaps one race will never fully rotate is bound to prematurely fail and that an alternate such as a spherical rose-joint would be more suitable albeit they would require some form of flexible boot to reduce dust ingress.

That said this type of joint is commonly used on race car suspension joints which are exposed to significant contaminants and also extensively used in the linkages used to articulate flight control surfaces in aeroplanes where airframe flexure needs to be accommodated.
In the former use-case you just live with the fact that these joints will wear and require frequent replacement and it is for this reason they are prohibited to being fitted to road going vehicles.
Is the mass of the arm relevant - I imagine the inertia from oscillation is quite high in this use-case and that perhaps aluminium may not offer much advantage longevity-wise.
WRT how to cut a hole accurately - as others have stated drilling undersize and reaming to size would be one route, the other if you had access to lathe would be to cut to finished dia using a boring bar.
I can't help but feel that replacing the bearing with an oiltite or spherical one would be a better solution - good luck!

 

[user 42626]

Not sure I would trust the Loctite in this application, narrow bearing in a through hole rather than a pocket. In any case it's about quality, if you are going to do it, do it right. Only ever used the Loctite in old machines where housings were a bit iffy.
In the OP's case I would say 4 years for a bearing like that, in that application is probably not unreasonable. £50 for the part is outrageous, so I can certainly see the attraction of making replacement ones in alloy.

Thanks for the support, whilst I'm not experienced with pricise engineering, I've done plenty of fabrication work in steel etc.
The logic makes sense, hardcore engineering and opinions are beyond my scope or attempts here but mentions of reamer bits and step cutting are all fairly simple. I'm hardly going to take over the world with this but a nicely done replacement is definitely something i believe can be done.

 

[Spectric]

but the link is for use on a scroll saw and will be exposed to constant wood dust

You can get boots, but not sure how much wear saw dust would cause as we used them on motorsport suspension without issues.

 

[user 42626]

My plan is not to follow a rose joints approach as i think the existing link system works perfectly. The wear over time is inevitable and even a rose joint will wear. Even with a boot fitted wood dust will enter, wood dust is like talc and it'll be in there without fail.
The alloy part can be oversize slightly and should give option to replace the bearing in the future or at least thats my plan,

 

[budgie98]

If the 16mm part is too short to go through, it might not cost all that much to have the bigger diameters above the 16mm portion ground down to 16mm so you achieve the depth you need.

Just grind off the bigger diameters: you only really need the 16mm cutting edge.

 

[Fergie 307]

Thanks for the support, whilst I'm not experienced with pricise engineering, I've done plenty of fabrication work in steel etc.
The logic makes sense, hardcore engineering and opinions are beyond my scope or attempts here but mentions of reamer bits and step cutting are all fairly simple. I'm hardly going to take over the world with this but a nicely done replacement is definitely something i believe can be done.

I would be inclined to experiment with one where the rotating joint is a bearing, but use an oilite or rose on the rocking one. Obviously that would be a long experiment, maybe in a saw of your own.
Having said that I can certainly see the attraction of presenting the customer with a better quality version of what they are used to.
A 5/8 drill followed up by an adjustable reamer would do it, but you need to make sure it goes in perpendicular, so the hole has parallel sides. The ones I use have plain bars at either end, if you could find one like that you could mount it in the drill chuck to keep it in line, then just turn the chuck by hand. Tighten the reamer up a little at a time until you reach the correct size. If you then lock it you can repeat that size over and over again. Bear in mind the alloy will get hot when you drill it, and expand. Better to wait till it gets cold again before reaming. You can buy a suitable sized chamfer tool to finish the edge of the hole and help start the bearing on its way.
Aluminium has a little give so the hole doesn't need to be as precisely sized as it would in steel for example. It does need to be tight enough that it needs to be pressed in properly with a tool. You could push them in using a vice if need be, an arbour press would be better.
Once you have the hole it would be a simple matter to make a jig with a pin the plate fits over so you can then round the ends up neatly on a belt or similar to whatever desired diameter. All quite labour intensive, but it's your time and if you are happy with that then fair play. And all you are going to be buying is the drill bit, reamer and chamfer tool, so not too great an outlay.
This type work best in aluminium, and don't forget the paraffin !