Diehead & Chaser Seminar

Setting Chaser Ahead For Grinding

Remove chasers and blocks from the dieheads and check the face reading on Micrometer Setting Gauge. Put the gauge in a vice, back off barrel A and remove chaser screw with a wrench.

Lift the chaser off the double serrated bushing, holding the bushing in the block by pushing wrench through the chaser screw hole. Carefully move the bushing one serration ahead in the block and replace the chaser on the bushing so the cutting edge of the chaser is near its former position on the block. This results in advancing the cutting edge of the chaser approximately .008” for each serration the bushing is moved ahead in the block.

What has actually been done to obtain this fine setting is to move the smaller end of the bushing ahead in the block, and the chaser back on the larger end of the bushing. For example, 1/4”-28 T.P.I. Chasers for a 3/8” Style DR diehead use a bushing with 19 serration on the small end (which goes in the block) and 20 serration on the large end (on which the chaser fits). Movement of one of the 19 serration is about .165”, and one of the 20 serration is about .157”. Thus, moving the bushing ahead .165” and the chaser back .157” leaves the chaser advanced .008” over its original position.


Check the chaser setting with micrometer barrel A to see that the chaser has been advanced enough to secure a good, clean grind. If more than a .008” grind is required moving chaser and bushing each two serration with advance the cutting edge .016”, and so on. Replace the chaser screw and as you tighten it, pull the chaser back against the bushing serration with “C” spanner wrench. This prevents movement of the chaser on its bushing under cutting pressure after it is replaced in the head.

*Keep chasers and block free from dirt and swarf.
RSVP Tooling Link Icon Additional Seminar Information

1. Seminar Outline
2. RSVP Tooling, Inc. - Information Sheet
3. Diehead Maintenance Check List
4. RSVP DR Diehead Parts List
5. Using The Micrometer Setting Gauge
6. How To Grind Circular Chasers
7. Setting Chaser Ahead For Grinding
8. Setting The Grinding Fixture
9. Grinding The Chaser

10. Useful Hints On Chaser Care & Threading
11. Problem Solving
12. Guide To Checking Block Wear
13. Micrometer Barrel Certification
14. Suggested Grinds - 4 Per set Straight
15. Suggested Grinds - 5 Per set Straight
16. Suggested Grinds - Taper
17. Chart For Micrometer "AA" Readings

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