Thread: HM 52 quill slot

Thanks for posting these measurements Dave. Good idea to put them here so everyone can see.

Just so everyone knows the background of this information/diagrams - I asked Dave for measurements from his HM-52B to allow me to replicate the anti-twist feature found on his quill. It consists of a pin installed in the side of the head (pic 1) that runs in a slot machined into the side of the quill (pic 2 gives its location).

Another job for you Mark, lol

I have done all these mods over the last year and a half to this mill, but I had 2 other mills the same over a 2 year period before that were I came up with the ideas. I am glad I waited to do these mods, because the other 2 went back to the seller with faults.

The screws that hold the pin into the head are M5 countersunk phillips head.

Dave

ummm
how can I machine it if its not in the machine?
or
If its in the machine how do I do it?

or
do I have to wait till I pull it apart, and take it to the machine shop I use for repairing shafts etc?

I asked Dave for advice on how to accomplish this task in some PM's I sent him. I have included his advice below, from a PM.

If you were to put one in you would have to sit the quill and the down feed gear back in, rotate the quill left to right on the gear to find the centre. Clamp up the quill then drill a hole undersize (I could give you measurements) through the casting into the quill enough to mark it. Then you could take it apart again and machine the slot and drill out the housing to suit your slot size. The pin has a head on it that is countersunk into the head so you would have to bore it again to suit your pin.
To do the boring you could take the rest of the head off and bolt it to the table.

Back to my thinking. To machine the slot in the quill you would use the horizontal spindle. You could mount the quill flat on the table and use a side cutter, vertically and use an end mill in a collet chuck or hoizontally and use an end mill in a collet chuck. The setup would need to be very accurate either way. For the boring of the hole for the pin in the head - once you have removed the head and bolted it to the table - it could be done with the horizontal spindle, and a collet chuck.

If I have misrepresented your advice in any way Dave, please correct me. I dont want people thinking the your advice is incorrect if it is my interpretation at fault.

Dave J - could you possibly take a photo of the pin plate/assembly installed on the head, and another photo of the back of the pin plate once removed(if it is simple to remove)? I am a bit confused as to the shape of the pin where it inserts into the head. I have a picture of it being tapered at the point where it contacts the head. I imagine this is the 25.5mm dimension on the drawings you provided. Could you confirm please?

I forgot I had horizontal ability...duh!!
thanks for reminding me Mark

Mark,Here are some more pictures for you.
The only thing I will add is to use a 6mm slot mill. mill down the middle then raise the knee for one side of the slot and lower it for the other, this is were the dro will come in handy, just make sure you tighten the gib locks with the same pressure each time you move the knee to make things accurate. I would make the pin to suit after the slot is cut, that way it can be trial fitted, I would go with a tight fit as it will wear in.
You can see in the photos the head counter sink has 4 holes, the 2 horizontal ones are factory stuff ups that went in at 30deg with stripped screws so I redrilled them vertical and put in new screws.

Ray, This might interest you.
I have got the quill pulled down on my mill at the moment because I am going to sleeve it with a cast iron bore, instead of just having 2 x 20-25mm collars holding it inside.
What I have found is that it was roughly honed when I got it and had high spots, after a bit of wear over the last 1 1/2 years it has worn those high spots down and I have a fair bit of slop in the quill (cant remember the number). Also when I tighten the quill lock it pushes the quill to the back and puts it out of tram in the Y axis.
I have sourced a sleeve from a motor rebuilder just have to pick it up.
I first got the idea looking at an old motor I was going to scrap and found a car bore is around the 89.95mm I need. More on this in another thread when I do it.

Eskimo
The horizontal comes in handy a lot for just using a collet chuck. It makes it easy for those impossible set ups in the vertical.

Dave

Thanks for the photos Dave. Clears up all the questions I had - but it has given me more. It looks like there is an internal thread in the outside end of the pin - in the centre of the actual protrusion - is that right? If so - what is its purpose? Is it to retract the pin from the head?

Are you going to bore out the collars to fit the sleeve you will installing using your horizontal spindle? Or are you going to outsouce this job? Will you skim the quill first to make it round again?

Hi Mark,
Yes that M5 threaded hole was in there, I think like you that it is to get the pin out. I have used it each time I took it out and it makes things easy. I cant see other reason for it be there.

Not sure which way to go, I am going to have a talk to the shop to see what price they will do it for, because after all they do this every day of the week.
If they want to much I will do it with the horizontal spindle with a boring head.
The inside head collars will need to be bored out to suit the new sleeve. The new collars are finished on the outside but not the inside, you have to bore them to suit after there fitted. The hole for the pulley bearings at the top has to line up as well or the spindle splines will ride on one side. It looks like the factory bores all 3 holes together. The Y axis does not have enough travel for all 3 even with the extension.
The quill lock and quill drive gear holes will be bored after the sleeve is installed.

The dovetail mill drill heads are built better than these as they have a cast sleeve that the quill runs in not just 2 collars. The style of mill is available with a mill drill head from China manufactures.

Just to confuse things,
I have added some pictures below that I got from a guy on PM.
It is a quill lock that locks into the slot of the quill, instead of pushing the quill to one side as these mill do. Not sure if I will go that way, I am looking into it to see if I can fit something like this together with the new sleeve.

Dave

Hi Dave,
I bought a HM52G about 9 months ago and today finally got around to testing it. To my horror the run out in the spindle is about 0.65 mm . There is also about 0.5 mm of vertical play between the spindle and the quill . I want to try and remove the quill to see when the problem is . Would you be able to post me detailed instruction and how to remove the quill.
Cheers Peter

Hi Peter,
Are you sure about that 0.65mm number? Thats huge, your cutters would only be cutting on one tooth.

Stuart

Hi Peter,
These mills are not the best considering what they charge, but with a few mods it makes a big difference.
To remove the quill you will first need to clamp the quill in the up position with the quill lock and then take off the chrome cover (on the left hand side standing in front of it) which is one Phillips head screw.
Once that is off place a small screw driver in one of the holes and undo the screw that goes up from under the head on that side. It doesn't need to be undone all the way, just enough to disengage it from the collar.
It will try to spin so maybe wear a glove, then once the pressure is off remove it.

You can the undo the little knob in the centre of the down feed handle on the other side (right hand side) and remove it. There is also a spring behind this.
Once that is done remove the 3 Allen head bolts and remove the fine down feed housing. It will have 2 dowel pins in it so it may take a little levering to get it off, or some have a M3 thread in the centre so you can screw in a bolt and lever it out.
When you remove that you can then undo the screw under the head on the right side and withdraw the gear shaft.

With all that out of the way you are ready to take the quill out. If it has the slot talked about in this thread you will need to undo the 2 screws on the left hand side to remove the pin set up going into the quill.
The quill if pretty heavy, so place a a block of wood on the table so it doesn't come crashing down when you release the quill lock. You can also place a piece of wood on the table and wind the knee up until it's touching, undo the quill lock, then wind the knee back down so it's taking the weight for you.

It takes longer to type than to do.

When your putting it back together you can tension the quill spring to suit what you like. The Bridgeport manual recommends it should pretty well balance it's self with your heaviest tool in the spindle. Where a drill press will return with some force.
I have mine set up like this and it suits me.

There are a few other threads on mods like changing the top bearing over to a taper bearing. It's a mod that I think does help, because the standard deep groove bearing is getting a lot of side thrust with any preload on the bearings.
https://www.woodworkforums.com/f65/ch...e-hm52-126514/

This is an easy fix for the bad fitting rattly spines
https://www.woodworkforums.com/f65/an...s-mill-126490/

https://www.woodworkforums.com/f65/nt...panner-121506/

https://www.woodworkforums.com/f65/hm...-280mm-121517/

https://www.woodworkforums.com/f65/in...6-17-a-116608/

If I missed something or you need more help, just let me know.
Dave

Hi Stuart, Dave
yes that right 0.65mm as measured with a dial gauge on the inside edge of the BT30 cone on the spindle. I did not didn't ever bother to try mounting a cutter to test it. I mounted the drill chuck and a 13 mm bit and it is so far out of center that the end of the bit moves several mm.

Dave
Thanks a lot for the detailed description on removing the quill. I was stuck on removing the spring I assumed screws holding the collar were a grub screws and was trying to loosen them with an allen key I will give it another go on the weekend with a small screw driver and that should solve the problem. I've decided to follow your advice and change the top bearing to a taper bearing. I will post some photos of the work as It progresses. Thanks again for your help and good advice.
cheers Peter

Hi Chaps

Just joined the forum, and greatly appreciate all the info and advice on the HM52. I have already made a big improvement in the surface finish on some trial pieces after removing the quill assembly... the taper bearing was quite dry ( obviously I haven't been pumping enough oil into it ), but at this stage I have just re-installed it with a good load of grease until I can get new bearings.

I also noticed that the locking tab washer was badly distorted and I suspect that it jammed up the thread for the adjuster nut and the taper bearing was never adjusted properly in the first place.It seemed to be running very freely, and after I re-greased it and made sure the nut and washer were running freely on the thread I got about another quarter turn before I was satisfied with the taper set-up.

I did have a couple of small issues in getting the quill out. My mill is about eighteen months old, and this may not apply to earlier models, but to release the round casting for the return spring, I had to dig a whole load of the epoxy putty they use to dress up the rough castings out of the hole before I could locate the locking screw , which in my case was a grub screw buried under the gunk and needed a 5/32 allen key to undo.

Then the gear shaft didn't want to come out and I eventually discovered another grub screw in a corresponding position on the RHS, this time engaging with a slot in the gear shaft. Again, the hole was partly full of epoxy putty which had to be scraped out before I could withdraw the screw and release the shaft. Just for a change , this one had a straight screwdriver slot!!

Will try and attach a couple of photos for anyone having similar problems..

Cheers

Paul
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